In the processing of bulk materials, including wet fibrous materials, it is often necessary to compress the materials to extract liquids and that is typically done with a screw press, which includes a screw operating within a cylindrical screen housing. As the screw compresses the fibrous materials by compacting them, liquid is expressed through the screen housing of the screw press. Each flight (360 degree wrap of flighting) of a screw can hold a certain volume of material as determined by its inner and outer diameter as well as its pitch (length). The compression ratio of the screw press is determined by dividing the volume of the flight entering the screen housing by the volume of the flight leaving the screw housing on the other side. In the compression of wet corn fiber materials, it is desirable to use an optimum compression ratio between one which results in escape of fibrous solids through the screen housing and a smaller compression ratio which results in too little liquid being extracted. Because compressed fibrous materials must be dried, remaining liquids must be removed through evaporation accomplished thermally by use of rotary dryers. Because it is far more enemy efficient to remove liquid mechanically through use of a screw press than thermally in a dryer, it is important to maximize compression without exceeding the limit which results in solids being forced through the cage structure. Generally, in the processing of wet corn fiber material, a nominally approximate compression ratio is 7.5 but materials vary and so use of that ratio may not be optimum for each processing site or each batch of material to be dewatered. However, varying the compression ratio of a screw press has heretofore only been accomplished by alteration of the pitch of the screw flighting at either the intake end or the outlet end, which necessarily requires disassembly of the screw press and reworking of the screw flighting. This is both time consuming and costly yet still typically yields only compromised results.
A need exists for an apparatus which allows variation in the compression ratio of a screw press without the need to alter the pitch of the screw on the intake end; preferably while the press is in operation